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From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Larysa Zaremba <larysa.zaremba@intel.com>,
	John Fastabend <john.fastabend@gmail.com>
Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
	andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
	yhs@fb.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org,
	David Ahern <dsahern@gmail.com>, Jakub Kicinski <kuba@kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Anatoly Burakov <anatoly.burakov@intel.com>,
	Alexander Lobakin <alexandr.lobakin@intel.com>,
	Magnus Karlsson <magnus.karlsson@gmail.com>,
	Maryam Tahhan <mtahhan@redhat.com>,
	xdp-hints@xdp-project.net, netdev@vger.kernel.org
Subject: [xdp-hints] Re: [PATCH bpf-next v2 15/20] net, xdp: allow metadata > 32
Date: Mon, 10 Jul 2023 16:01:02 +0200	[thread overview]
Message-ID: <8821258e-08e7-8128-8275-74ce550110cd@intel.com> (raw)
In-Reply-To: <ZKbU6qaPUN/gPY9t@lincoln>

From: Larysa Zaremba <larysa.zaremba@intel.com>
Date: Thu, 6 Jul 2023 16:51:22 +0200

> On Mon, Jul 03, 2023 at 02:06:46PM -0700, John Fastabend wrote:
>> Larysa Zaremba wrote:
>>> From: Aleksander Lobakin <aleksander.lobakin@intel.com>
>>>
>>> When using XDP hints, metadata sometimes has to be much bigger
>>> than 32 bytes. Relax the restriction, allow metadata larger than 32 bytes
>>> and make __skb_metadata_differs() work with bigger lengths.
>>>
>>> Now size of metadata is only limited by the fact it is stored as u8
>>> in skb_shared_info, so maximum possible value is 255. Other important
>>> conditions, such as having enough space for xdp_frame building, are already
>>> checked in bpf_xdp_adjust_meta().
>>>
>>> The requirement of having its length aligned to 4 bytes is still
>>> valid.
>>>
>>> Signed-off-by: Aleksander Lobakin <aleksander.lobakin@intel.com>
>>> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
>>> ---
>>>  include/linux/skbuff.h | 13 ++++++++-----
>>>  include/net/xdp.h      |  7 ++++++-
>>>  2 files changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>>> index 91ed66952580..cd49cdd71019 100644
>>> --- a/include/linux/skbuff.h
>>> +++ b/include/linux/skbuff.h
>>> @@ -4209,10 +4209,13 @@ static inline bool __skb_metadata_differs(const struct sk_buff *skb_a,
>>>  {
>>>  	const void *a = skb_metadata_end(skb_a);
>>>  	const void *b = skb_metadata_end(skb_b);
>>> -	/* Using more efficient varaiant than plain call to memcmp(). */
>>> -#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
>>
>> Why are we removing the ifdef here? Its adding a runtime 'if' when its not
>> necessary. I would keep the ifdef and simply add the default case
>> in the switch.
> 
> Seems like Alex has missed your message, but we discussed this with him before, 
> so I know the answer: Compiler will 100% convert it into a compile-time 'if' and 
> this looks nicer than preprocessor condition.

Sorry, I'm not always able to follow all the threads =\

As Larysa said, it's not a runtime `if`. Both conditions are always
known at compilation time.
And this looks a bit less ugly than with ifdefs to me :D

Thanks,
Olek

  reply	other threads:[~2023-07-10 14:04 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-03 18:12 [xdp-hints] [PATCH bpf-next v2 00/20] XDP metadata via kfuncs for ice Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 01/20] ice: make RX hash reading code more reusable Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 02/20] ice: make RX HW timestamp " Larysa Zaremba
2023-07-04 10:04   ` [xdp-hints] " Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 03/20] ice: make RX checksum checking " Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 04/20] ice: Make ptype internal to descriptor info processing Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 05/20] ice: Introduce ice_xdp_buff Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 06/20] ice: Support HW timestamp hint Larysa Zaremba
2023-07-05 17:30   ` [xdp-hints] " Stanislav Fomichev
2023-07-06 14:22     ` Larysa Zaremba
2023-07-06 16:39       ` Stanislav Fomichev
2023-07-10 15:49         ` Larysa Zaremba
2023-07-10 18:12           ` Stanislav Fomichev
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 07/20] ice: Support RX hash XDP hint Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 08/20] ice: Support XDP hints in AF_XDP ZC mode Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 09/20] xdp: Add VLAN tag hint Larysa Zaremba
2023-07-03 20:15   ` [xdp-hints] " John Fastabend
2023-07-04  8:23     ` Larysa Zaremba
2023-07-04 10:23       ` Jesper Dangaard Brouer
2023-07-04 11:02         ` Larysa Zaremba
2023-07-04 14:18           ` Jesper Dangaard Brouer
2023-07-06 14:46             ` Larysa Zaremba
2023-07-07 13:57               ` Jesper Dangaard Brouer
2023-07-07 17:58                 ` Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 10/20] ice: Implement " Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 11/20] ice: use VLAN proto from ring packet context in skb path Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 12/20] xdp: Add checksum level hint Larysa Zaremba
2023-07-03 20:38   ` [xdp-hints] " John Fastabend
2023-07-04  9:24     ` Larysa Zaremba
2023-07-04 10:39       ` Jesper Dangaard Brouer
2023-07-04 11:19         ` Larysa Zaremba
2023-07-06  5:50           ` John Fastabend
2023-07-06  9:04             ` Jesper Dangaard Brouer
2023-07-06 12:38               ` Larysa Zaremba
2023-07-06 12:49                 ` Larysa Zaremba
2023-07-10 16:58                   ` Alexander Lobakin
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 13/20] ice: Implement " Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 14/20] selftests/bpf: Allow VLAN packets in xdp_hw_metadata Larysa Zaremba
2023-07-05 17:31   ` [xdp-hints] " Stanislav Fomichev
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 15/20] net, xdp: allow metadata > 32 Larysa Zaremba
2023-07-03 21:06   ` [xdp-hints] " John Fastabend
2023-07-06 14:51     ` Larysa Zaremba
2023-07-10 14:01       ` Alexander Lobakin [this message]
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 16/20] selftests/bpf: Add flags and new hints to xdp_hw_metadata Larysa Zaremba
2023-07-04 11:03   ` [xdp-hints] " Jesper Dangaard Brouer
2023-07-04 11:04     ` Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 17/20] veth: Implement VLAN tag and checksum level XDP hint Larysa Zaremba
2023-07-05 17:25   ` [xdp-hints] " Stanislav Fomichev
2023-07-06  9:57     ` Jesper Dangaard Brouer
2023-07-06 10:15       ` Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 18/20] selftests/bpf: Use AF_INET for TX in xdp_metadata Larysa Zaremba
2023-07-05 17:39   ` [xdp-hints] " Stanislav Fomichev
2023-07-06 14:11     ` Larysa Zaremba
2023-07-06 17:25       ` Stanislav Fomichev
2023-07-06 17:27       ` Stanislav Fomichev
2023-07-07  8:33         ` Larysa Zaremba
2023-07-07 16:49           ` Stanislav Fomichev
2023-07-07 16:58             ` Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 19/20] selftests/bpf: Check VLAN tag and proto " Larysa Zaremba
2023-07-05 17:41   ` [xdp-hints] " Stanislav Fomichev
2023-07-06 10:10   ` Jesper Dangaard Brouer
2023-07-06 10:13     ` Larysa Zaremba
2023-07-03 18:12 ` [xdp-hints] [PATCH bpf-next v2 20/20] selftests/bpf: check checksum level " Larysa Zaremba
2023-07-05 17:41   ` [xdp-hints] " Stanislav Fomichev
2023-07-06 10:25   ` Jesper Dangaard Brouer
2023-07-06 12:02     ` Larysa Zaremba

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